Big asteroid to flash by earth, but will miss

In just about a week, an object flying at eight times the velocity of a high-speed rifle bullet, and with the explosive potential of 2.4 million tons of TNT, will zip past the earth so close that it will fly within the orbits of communications and navigation satellites.

But NASA scientists say it poses no risk to our planet. The object, asteroid 2012 DA14, was discovered almost exactly a year ago by a team of sky-watchers in Spain.

In a teleconference conducted Thursday, a group of NASA's top scientists spent an hour telling the world's press the precise orbit of the roughly 150-foot-diameter rock has no chance of hitting earth.

Speaking from his office in Pasadena, Donald Yeomans, manager of the Near Earth Object Office, Jet Propulsion Laboratory, confidently predicted the asteroid, at its closest approach, will pass between 17,100 and 17,200 miles over Indonesia in the dark of Feb. 15.

At that closest approach, the asteroid will be too dim to be seen with the naked eye and its extreme speed would make it hard to observe even if one could find it in the heavens.

The scientists say Australia would be the best place to view DA14, but that would require a sophisticated telescope.

Yeomans said even though the asteroid poses no danger to earth, it still is a record breaker because it is the largest object ever observed this close to earth.

He said NASA believes an asteroid does a near-earth flyby about once every 40 years and one hits the earth about once every 1,200 years, but rocks the size of this asteroid are rare.

Lindley Johnson, program executive, Near-Earth Object Observations Program, NASA Headquarters, Washington D.C., said if the object was on a slightly different trajectory and did hit earth, it would not have caused a planetary disaster, but it would have done a lot of damage regionally.

She said the effect of DA14 hitting earth would have been similar to the so-called "Tunguska event."

In June of 1908, an object detonated in the air over remote Siberia, near the Tunguska River.

Yeomans said that blast knocked down trees over about 800 square miles.

Amy Mainzer, principal investigator for one phase of the Near-Earth Object project, said DA14 probably came from a belt of asteroids between Mars and Jupiter.

For the most part, these asteroids are in "stable" orbits, according to Mainzer, but sometimes something kicks one out of the asteroid belt in such a way that it begins the long journey toward earth.

Mainzer said she will be involved in using radar and telescopes using the infrared spectrum, to get precise size measurements as well as data on the makeup of DA14.

The NASA scientists said calculations suggest the asteroid has been circling the sun on roughly the same one-year cycle as the earth, but the gravitational attraction of the earth during next week's pass will shift the rock's orbit.

After that, the orbits of the earth and DA14 will be dramatically divergent.

NASA has a range of facilities around the globe that nightly search the sky for asteroids. When there's an object of the size of this asteroid, with a trajectory that brings it into the earth's neighborhood, it is subjected to intense scrutiny to determine whether it is a threat or just a passing visitor.

Johnson said NASA and other partners around the globe have identified about 10,000 such objects over the last 15 years of concerted study, and the space agency predicts that might be as much as 10 percent of the total asteroids out there.